Method of making brake shoes



Aug. 25, 1959 R. L. WILSON 2,900,711

METHOD OF MAKING BRAKE SHOES Filed Aug. 29, 1956 INVENTOR. ROSSER L. WILSON ATTORNEYS METHOD OF MAKING BRAKE SHOES Rosser L. Wilson, Mahwah, N.J., assignor to American Brake Shoe Company, New York, N.Y., a corporation of Delaware Application August 29, 1956, Serial No. 606,863

2 Claims. (Cl. 29-407) This invention relates to a method of making railroad braking systems and is particularly concerned with a method of constructing and maintaining railroad braking systems which precludes substitution of one type of brake shoe for another.

The brake shoe which has long been standard in the railroad industry comprises a cast iron body having a substantial thickness and having a braking surface which is curved to correspond in general to the curvature of a railroad car or locomotive wheel. The dimensions and configuration of the cast iron shoe have long been standardized in the railroad industry in accordance with standards established by the American Association of Railroads. Each brake shoe includes a pair of end stops located at opposite ends of the back or convex surface of the shoe and a pair of toe guides extending from the end stops toward the center portion of the shoe. An attaching lug is positioned in the center portion of the brake shoe back, and, in conjunction with the other mounting lugs comprising the end stops and toe guides, is utilized in mounting the brake shoe upon a brake head. The standard brake head upon which the cast iron shoe is mounted includes an attaching lug recess into which the center attaching lug of the brake shoe is fitted. A portion of the brake head engages the convex surface of the brake shoe, and the extremities or toes of the brake head engage the end stops of the brake shoe and also provide a pair of recesses into which the brake shoe toe guides are fitted.

It has been proposed that composition type brake shoes be substituted for cast iron shoes in at least some railroad braking applications. These composition type shoes, which include a brake body of a composition material and a metal back or support structure, provide a substantially higher retarding force per unit area of the braking surface than the standard cast iron shoes, due to the fact that the composition material afiords a substantially higher coeflicient of friction when brought into contact with the wheel of a railroad car or locomotive than may be obtained with a cast iron shoe. In general, it may be stated that cast iron shoes are high-pressure low-friction devices, whereas composition shoes are highfriction low-pressure devices. Accordingly, the composition shoes may be operated at substantially lower braking pressures than the cast iron shoes and it is usually desirable to incorporate substantially smaller actuating cylinders in a system adapted for use of composition shoes, due to the lower pressure requirements.

The mounting arrangement embodied in standard cast iron shoes and standard brake heads has been tested and proved for reliability and strength over many years of operation; consequently, it is highly desirable to utilize an essentially similar arrangement in mounting composition shoes in a railroad braking system. Moreover, for practical reasons, it is desirable that the composition shoes be of approximately the same size as cast iron shoes in order to minimize any necessity for substanatent ice tial revision or redesign of other components in the braking system or of other related parts of railway cars and locomotives equipped with composition shoe brakes. On the other hand, a substantial danger is presented if it is possible for railroad maintenance personnel to substitute cast iron shoes for composition shoes or to replace composition shoes with cast iron shoes. Cast iron brake shoes, when substituted in a braking system constructed for use with composition shoes, provide inadequate braking and consequently may seriously endanger the railroad equipment, passengers, freight, and/or other property. Incorporation of composition shoes in a sys tem adapted for use of cast iron shoes, on the other hand, may give irregular and unbalanced braking it the replacement is not complete in all cars, may lead to burning out of the brake shoes, and may cause damage by virtue of excessively abrupt stops. Consequently, composition shoes, when incorporated in a system designed and constructed for use of cast iron shoes, create dangers of the same magnitude as those involved in the substitution of cast iron shoes for composition shoes.

It is an object of the invention, therefore, to prevent interchange of cast iron and composition brake shoes in a railroad braking system by resort to a specific method of constructing and maintaining the railroad braking system.

A further object of the invention is a new and improved method of preventing interchange of cast iron and composition brake shoes in railroad braking systems which is inherently immune to errors on the part of maintenance personnel.

It is an important object of the invention to prevent interchange of cast iron and composition railroad brake shoes between braking systems while simultaneously retaining all of the advantages and desirable characteristics of standard brake shoe mounting maintenance procedure.

It is an additional object of the invention to afford a method of constructing and maintaining railroad braking systems which is inherently economical yet effectively prevents substitution of one type of brake shoe in a system constructed for use of another type.

Accordingly, the invention relates to the manufacture and construction of railroad braking systems and to a method of preventing substitution of cast iron brake shoes or composition type brake shoes in a braking system constructed for utilization of the other type of shoe. In accordance with the invention, a plurality of mounting lugs corresponding in number and position to the lugs on a standard cast iron shoe are afiixed to each of the composition shoes. One of these mounting lugs is constructed with a first critical mounting dimension substantially larger than the corresponding standard dimension on a cast iron shoe and one of the lugs is fabricated with a second integral mounting dimension substantially smaller than the corresponding standard dimension. In addition, each of the brake heads for use in a compositiontype shoe system is constructed with a plurality of lugengaging elements substantially corresponding to the lugengaging elements of the standard brake heads; these specialized brake heads, however, are modified to include first and second critical lug-engaging dimensions individually corresponding to the aforementioned first and second critical mounting lug dimensions. Thus, the special composition shoes are prevented from being mounted in standard brake heads by virtue of the enlarged first critical dimension, whereas the specialized brake heads cannot accept a standard cast iron shoe due to the reduced second critical dimension.

Other and further objects of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawing which, by way of illustration, shows a preferred embodiment of railroad braking equipment which may be employed to carry out the method of the invention. The principles of the invention are set forth fully in the description and claims; other embodiments of the invention embodying the same and equivalent principles may be used and structural changes in the devices to which the inventive method is applied may be made as desired by those skilled in the art without departing from the invention and the purview of the appended claims.

In the drawings:

Fig. 1 is an elevation view, partly cut away, of a railroad brake head;

Fig. 2 is an elevation view of a composition type railroad brake shoe adapted for mounting in the brake head of Fig. 1;

Fig. 3 is a plan view of the brake shoe of Fig. 2;

Fig. 4 is a sectional view of the brake shoe, taken along line 44 in Fig. 2; and

Fig. 5 is a detail sectional view of a portion of the brake head taken along line 5-5 in Fig. 1.

The brake head illustrated in Fig. 1 is in most respects essentially similar to a standard brake head constructed for use with standard cast iron brake shoes. Brake head 10 comprises a concave surface 11 which is shaped to engage the convex surface of a brake shoe and which is interrupted in the center portion to form a lug-receiving receptacle 12. In general configuration and location, lug-receiving portion 12 of the brake head is essentially similar to the corresponding part of a standard brake head, although it varies from standard construction in one significant respect as will be explained more completely hereinafter. The brake shoe engaging surface 11 is continued into the toe sections 13 and 14 of the brake head. Toe section 13 includes a bearing surface 15 adapted to engage the end stop of a brake shoe in the usual manner, and a similar end stop engaging surface 16 is provided on toe 14 of the brake head. Each of toes 13 and 14 is bifurcated to provide a receptacle into which the toe guide of a brake shoe may be fed, as indicated by the cut away portion of toe section 14 and shown in detail in Fig. 5.

The composition type railroad brake shoe 20 illustrated in Fig. 2 comprises a metal support member 21 and a composition body 22 which is mounted on the support member. Support member 21 is preferably formed from hot-rolled steel, and composition body 22 may be manufactured from any composition material suitable for use in railroad braking service. A preferred type of composition material, which exhibits superior characteristics with respect to heat and shock resistance and which affords a favorable ratio of wet to dry coefiicients of friction, is described and claimed in the co-pending application of Ray E. Spokes et al. Serial No. 491,510, filed March 1, 1955 and assigned to the same assignee as the present invention. This preferred composition comprises a comminuted friction material, selected from the sillimanite group and related aluminum silicates, distributed in a heat-stable elastomer binder; additional friction material in the form of cast iron particles may also be included.

Composition body 22 may be provided with two or more vents 23 in the braking surface thereof to assist in uniform curing of the composition throughout its thickness and to aid in the diffusion of heat during braking service. The composition body may be clamped to support member 21 by means of a pair of longitudinal flanges which engage the sides of the composition body and which are preferably formed as an integral part of support member 21; only one flange 24 appears in the drawing. Additional means for interlocking the composition body and metal support member may be provided as desired.

'Brake shoe 20 is provided with a center attaching lug 25 preferably fabricated from steel and mounted upon support member 21 in any suitable manner as by welding, clenching, or other means. In general, the position and configuration of center attaching lug 25, which is provided with the usual keyway 26, are similar to the location and configuration of the center attaching lug on a standard cast iron brake shoe. In addition, as best illustrated in Figs. 2 and 3, brake shoe 20 is provided with an end stop 27 at one end of support member 21 and a second end stop 28 at the other end of the support member. Each of end stops 27 and 28 comprises a lug projecting above the convex surface of the brake shoe support member and extending transversely of the support member. A first toe guide 29 projects from the convex surface of support member 21 adjacent end stop 27 and extends from the end stop toward the central portion of the brake shoe back. A similar toe guide 30 is provided at the end of support member 21 adjacent end stop 28. End stops 27 and 28 are positioned to engage bearing surfaces 15 and 16 of brake head 10, whereas toe guides 29 and 30 are adapted to engage in the receptacles provided therefor in the brake head toe sections, one of these receptacles 31 being illustrated in the detail sectional view of Fig. 5.

In general, as will be apparent to those skilled in the art, the construction of brake head 10 and brake shoe 20, as illustrated in Figs. 15, is quite conventional and is essentially similar to the construction long standard in the railroad industry. Brake shoe 20 may be mounted on brake head 10 by interfitting the two structures, with center attaching lug 25 engaging in the receptacle 12 of the brake head, brake head surface 11 engaging the convex surface 32 of the brake shoe, brake head surfaces 15 and 16 engaging end stops 27 and 28 respectively, and toe guides 29 and 30 engaging in the receptacles provided therefor in the brake head toe sections. Consequently, it will be apparent that if the dimensions and configuration of the mounting lugs of brake shoe 20, comprising center attaching lug 25, end stops 27, 28, and toe guides 29 and 30, are made to correspond to current standards and if brake head 10 is similarly constructed in accordance with standard dimensions, it should be possible to interchange the composition brake shoes with cast iron brake shoes. As pointed out above, however, interchangeability is totally undesirable, since it introduces the possibility of establishing extremely dangerous braking conditions. In accordance with the present invention, however, the dangers inherent in interchangeable construction are eliminated without losing any of the advantages of the proven standard mounting arrangement and without substantial increase in cost of either the brake shoe or the brake head.

In achieving this result, the following procedure is followed: each of the mounting lugs on the composition brake shoe is mounted in the same general position and has the same general configuration as the corresponding mounting elements on a cast iron brake shoe; one of these mounting lugs, however, is constructed with a first critical mounting dimension substantially larger than the corresponding standard dimension on a cast iron shoe. In addition, one of the mounting lugs on composition shoe 20 is made with a second criitcal mounting dimension sub stantially smaller than the corresponding standard dimension. In constructing brake head 10, on the other hand, the plurality of lug-engaging elements comprising the walls of receptacle 12, surface 11, and the various elements of toe sections 13 and 14 are made to correspond to the similar lug-engaging elements of a standard brake head but are modified to have first and second critical lugengaging dimensions individually corresponding to the aforesaid critical lug dimensions on brake shoe 20. By constructing the composition shoe 20 and the specialized brake head 10 in this manner, composition shoe 20 is prevented from being mounted in a standard brake head by virtue of the enlarged first critical dimension. Moreover, t e reduced second critical dimension prevents mounting of a standard cast iron shoe in specialized brake head 10.

There are a number of different dimensional combina tions which may be modified in accordance with the invention to achieve the desired objectives. One particular modification is illustrated in the drawing and comprises a variation in the dimensions of center attaching lug 25 and toe guides 29 and 30 with a corresponding modi fication of the critical dimensions of the elements on brake head which engage those lug members. As indicated in Fig. 1, the walls of center attaching lug receptacle 12 are separated by a predetermined distance 35; this critical dimension is made substantially larger than the corresponding critical dimension 358 of a standard shoe, which is shown in dotted outline at 128. For the dimensions and specifications of standard cast iron railway brake shoes, reference may be made to specification M40144 and drawing E-89-1938 of the Association of American Railroads. The corresponding critical dimension 36 of center attaching lug 25 (Fig. 2) is similarly made substantially larger than the standard dimension 368 of a cast iron brake shoe, the outline of the standard construction being indicated by dash lines 258. The mounting lug 25 of the composition shoe, having a width as indicated by dimension 36, cannot be fed into the lug receptacle 125 of a standard brake head having a maximum internal dimension 358, so that substitution of the composition shoe in a system adapted for use of cast iron shoes is prevented. Construction of the brake shoe and brake head in this manner, however, would not prevent mounting of a cast iron shoe in brake head 10; it is true that the shoe would fit somewhat loosely but it could be mounted in the specialized brake head and very probably would be substituted for the desired composition type shoe in at least some instances unless extreme and inordinate care were exercised in maintenance of the specialized braking system constructed for use of composition shoes.

In accordance with the inventive method, substitution of cast iron shoes in a specialized braking system designed for use of composition shoes may be prevented by aflixing to each of the composition shoes a toe guide having a maximum width 37 substantially smaller than the corresponding standard dimension 375 of a cast iron brake shoe, as indicated in Figs. 3 and 4 by forming in the toe extensions of brake head 10 a toe guide receptacle 31 having a corresponding critical dimension 38 which is substantially smaller than the corresponding standard dimension 38S, as shown in Fig. 5. The outline of a standard toe guide is indicated in Figs. 3 and 4 by dash lines 39 and the outline of a standard brake head toc guide receptacle is shown in Fig. 5 by dash lines 40. With this second modification, the inventive method precludes mounting of a standard cast iron brake shoe in specialized brake head 10, since a standard toe guide cannot be fitted into the receptacle 31 provided therefor on the brake head.

Considering an entire railway system, therefore, interchange of composition and cast iron brake shoes is prevented by a method of construction and maintenance which contemplates manufacturing and maintaining a stock of cast iron brake shoes and brake heads of standard dimensions and configurations. Composition type brake shoes, on the other hand, are fabricated with mounting lugs which correspond in configuration to the lugs of standard cast iron shoes and which are mounted in the same general positions but which have a first critical dimension larger than the corresponding standard dimension (dimension 36 in the illustrated apparatus) and a second critical dimension smaller than the corresponding standard dimension (dimension 37 in the drawing). In addition, each of the brake heads utilized with composition shoes is fabricated with lug-engaging elements corresponding to the lug-engaging elements of a standard brake head but with first and second critical dimensions modified with respect to standard dimensions in correspondence with the modifications of the brake head mounting lug dimensions as indicated by dimensions 35 and 38 in the drawing. The standard brake heads are installed on railway cars in operative connection with actuating equipment of standard construction and suitable for use with cast iron shoes. The specialized brake heads are similarly installed and connected to actuating equipment constructed for use with composition type shoes and usually including smaller braking cylinders than standard or with other modifications for providing the reduced braking pressures desirable with composition type shoes. The brake shoes are then selectively mounted on the brake heads in accordance with the requirements established by the critical dimensions of the brake heads and brake shoes; that is, the composition type shoes are necessarily mounted on the specialized brake heads, since they cannot be fitted on standard brake heads, and the standard cast iron shoes are installed in standard brake heads inasmuch as they will not fit the specialized brake heads.

There are a number of different possible combinations of critical dimensions which may be modified in accordance with the invention. For example, the selective and preventive features of the invention may be achieved by making center lug 25 of the composition brake shoe substantially narrower than standard dimension 36S and at the same time making toe guides 29 and 30 substantially wider than the standard dimension 378, in which instance corresponding modifications are made in the brake head 10. In this variation of the invention, the enlarged toe guides prevent mounting of composition shoes in a standard brake head, whereas the reduced size of the center attaching lug receptacles in the specialized brake heads preclude fitting cast iron shoes in a composition shoe system.

The same beneficial results may be achieved by making center lug 25 of the composition shoe wider than standard, as in the illustrated apparatus, and by reducing the length 41 of end stops 27 and 28 (see Fig. 2), thereby increasing the overall distance separating the two end stops. Under these circumstances, the change in dimensions of the center lug and center lug receptacle act as in the illustrated apparatus to prevent substitution of composition type shoes for cast iron shoes and the modification of the end stops with a corresponding modification of the toe sections 13 and 14 of the brake head prevents mounting of a cast iron shoe upon the specialized brake head, inasmuch as surfaces 15 and 16 of the brake head interfere with the end stops on a standard shoe. In some instances, it may be desirable to construct the components of the specialized or composition shoe system with center attaching lugs of standard dimensions and configuration, in which instance the toe guides and toe guide receptacles of the specialized system may be made narrower than standard and the end stops may be made longer, thereby requiring a reduction in the spacing of end stop engaging surfaces 15 and 16. Of course, this relationship may be reversed, making the specialized composition shoe toe guides wider and the end stops shorter than standard; similarly, the center lug of the composition shoe may be made narrower and the end stops longer than standard. Other combinations of critical modifications may be made; in each instance, it must be borne in mind that one of the departures from standard must serve to prevent mounting of the non-standard or composition type shoes in a standard brake head whereas the further modification must effectively prevent mounting of a cast iron shoe in the specialized brake head.

By following the procedure of the invention, all of the inherent advantages of the proven standard mounting arrangement are retained in a specialized braking system. No re-education of maintenance personnel is required since the brake shoes are fitted to brake heads in the same manner as standard equipment. At the same time,

human error is completely eliminated as a potential danger element in that it is made impossible to mount cast iron shoes in a braking system intended for use of composition type shoes and the substitution of composition shoes in a standard cast iron shoe braking system is completely avoided.

Hence, while I have illustrated and described the preferred embodiment of my invention, it is to be understood that this is capable of variation and modification, and I therefore do not wish to be limited to the precise details set forth, but desire to avail my self of such changes and alterations as fall within the purview of the following claims.

I claim:

1. In the manufacture of components for a specialized railroad braking system comprising a plurality of composition-type brake shoes subject to excessive wear and damage when incorporated in a standard system constructed for utilization of standard cast iron brake shoes, in which specialized braking system cast iron shoes provide inadequate braking, the method of fabricating component parts for said system to prevent substitution of standard cast iron shoes in said specialized system and to prevent incorporation of said composition-type shoes in a standard system comprising affixing to each of the composition-type shoes intended for use in said special ized braking system a plurality of mounting lugs corresponding in number and position to the lugs on a standard cast iron shoe, one of said mounting lugs having a first critical mounting dimension substantially larger than the corresponding standard dimension on a cast iron shoe and one of said lugs having a second critical mounting dimension substantially smaller than the corresponding standard dimension, and forming in each of the brake heads for said specialized system a plurality of lug-engaging elements corresponding to the lug-engaging-elcments of a standard brake head but having first and second critical lug-engaging dimensions individually corresponding to said first and second critical mounting lug dimensions, whereby said composition shoes cannot be mounted in standard brake heads by virtue of said enlarged first critical dimension and said specialized system brake heads cannot accept a standard cast iron shoe by virtue of said reduced second critical dimension.

2. In the manufacture of components for a specialized railroad braking system comprising a plurality of composition-type brake shoes subject to excessive wear and damage when incorporated in a standard system constructed for utilization of a standard cast iron brake shoe, in which specialized braking system cast iron shoes provide inadequate braking, the method of fabricating component parts for said system to prevent substitution of standard cast iron shoes in said specialized system and to prevent incorporation of said compositiontype shoes in a standard system comprising afiixing to each of the composition-type shoes intended for use in said specialized braking system a plurality of mounting lugs corresponding in number and position to the lugs on a standard cast iron shoe and including a center mounting lug, a pair of toe guides, and two pair of end stops, said center lug having a critical mounting dimension substantially different from the corresponding standard dimension on a cast iron shoe and said toe guides each having a critical mounting dimension substantially different from the corresponding standard dimension, a first one of said critical mounting dimensions being larger than the corresponding standard dimension and the sec ond of said critical mounting dimensions being smaller than the corresponding standard dimension, and forming in each of the brake heads for said specialized system a plurality of lug-engaging elements corresponding to the lug-engaging elements of a standard brake head but having first and second critical lug-engaging dimensions individually corresponding to said first and second critical mounting lug dimensions, whereby said composition shoes cannot be mounted in standard brake heads by virtue of said enlarged first critical dimension and said specialized system brake heads cannot accept a standard cast iron shoe by virtue of said reduced second critical dimension.

References Cited in the file of this patent UNITED STATES PATENTS 1,470,478 Pettis Oct. 9, 1923 

